A uniform distribution of a small amount of a liquid adjuvant on granular materials and finely particulate solids may be carried out, for example, to increase the solubility, to accelerate reaction and dissociation processes after suspension in solution, to improve the dispersability, the flow properties, the optical properties and to improve the taste and smell, to protect against humidity, oxygen, bacterial or fungal attack or for binding dust. Particularly in the case of granular dyes and dye powders, non-dusting behavior and flow behavior are becoming increasingly significant as quality parameters.
Processing a liquid adjuvant has the advantage, compared to an adjuvant in solid form, that liquid adjuvants are easier to distribute and that, because of the possibility of dilution, they can be applied in a controlled manner in extremely low concentrations.
Instead of admixing the granular material or the powder homogeneously with a liquid adjuvant it is possible to achieve the same effect, using a smaller amount of liquid adjuvant, by means of subsequent coating by spraying. On the grounds of product purity and cost minimization, too, the aim is to use an small amounts as possible of liquid adjuvants for coating and to distribute these as uniformly as possible.
In all applications, the quality of the coating depends on the dosage of the substances employed, the arrangement and construction of the feed device, the distribution of the coating agent, the mixing and the homogenization of the bulk material to be treated.